Many factors, including environmental responsibility efforts and modern environmental regulations on engine exhaust emissions, have reduced the allowable acceptable levels of certain pollutants that enter the atmosphere following the combustion of fossil fuels. Increasingly, more stringent emission standards may require greater control over either or both the combustion of fuel and post combustion treatment of the exhaust. For example, the allowable levels of nitrogen oxides (NOx) and particulate matter have been greatly reduced over the last several years. To address, among other issues, environmental concerns, many diesel engines now have a diesel oxidation catalyst (DOC) as well as a diesel particulate filter (DPF) within an exhaust system of the diesel engine purposed to reduce the amount of unburned hydrocarbons and particulate matter released into the atmosphere.
In some diesel engine operating conditions, such as operating conditions that produce low exhaust temperatures, unburned hydrocarbons may slip over the DOC and lodge within, or on a front face of the DPF. When a regeneration of the DPF is subsequently performed, these additional hydrocarbons may combust and cause the DPF to crack based on the additional heat from the burning of these hydrocarbons that had slipped over the DOC. Additionally, the DOC itself may sometimes become plugged with unburned hydrocarbons, such that the DOC is not functioning properly. Therefore, these unburned hydrocarbons may cause damage to both the DOC and the DPF, resulting in potentially expensive repairs.
Therefore, a need exists for a method of determining when unburned hydrocarbons are accumulating on or within the DOC and the DPF.